Supercharger control device for an internal combustion engine

Abstract

A supercharger control device for an internal combustion engine is preferably applied to a system having a first supercharger and a second supercharger. A switching supercharging pressure setting unit sets a switching supercharging pressure used in case of switching a mode for operating the first supercharger and the second supercharger, based on a difference between a target supercharging pressure and an actual supercharging pressure. When the actual supercharging pressure reaches the switching supercharging pressure, a switching control unit performs a control of switching the mode. Therefore, it becomes possible to appropriately prevent the overshoot of the supercharging pressure at the time of switching the mode.

The invention claimed is: 
     
       1. A supercharger control device for an internal combustion engine having a first supercharger and a second supercharger, comprising:
 an intake air amount detecting unit which detects an intake air amount; 
 an operating unit which operates the engine with only the first supercharger in a single turbo mode and operates the engine with both the first supercharger and the second supercharger in a twin turbo mode; 
 a target supercharging pressure determining unit which determines a target supercharging pressure based on a driving state of the engine; 
 an actual supercharging pressure detecting unit which detects an actual supercharging pressure; 
 a switching supercharging pressure setting unit which sets a basic switching supercharging pressure used for switching from the single turbo mode to the twin turbo mode based on the intake air amount; 
 a switching supercharging pressure correcting unit which corrects the basic switching supercharging pressure to determine a corrected switching supercharging pressure based on a supercharging pressure difference between the target supercharging pressure and the actual supercharging pressure; and 
 a switching control unit which controls the operating unit to switch an operation mode of the engine from the single turbo mode to the twin turbo mode when the actual supercharging pressure reaches the corrected switching supercharging pressure, 
 wherein
 the switching supercharging pressure correcting unit determines the corrected switching supercharging pressure to be a lower pressure when the supercharging pressure difference between the target supercharging pressure and the actual supercharging pressure is larger, and 
 the switching supercharging pressure correcting unit determines the corrected switching supercharging pressure to be a higher pressure when the supercharging pressure difference between the target supercharging pressure and the actual supercharging pressure is smaller. 
 
 
     
     
       2. The supercharger control device for an internal combustion engine according to  claim 1 ,
 wherein the switching supercharging pressure correcting unit corrects the switching supercharging pressure further based on a difference between the basic switching supercharging pressure and the target supercharging pressure. 
 
     
     
       3. The supercharger control device for an internal combustion engine according to  claim 1 ,
 wherein the switching supercharging pressure correcting unit corrects the switching supercharging pressure, based on a driving state of the internal combustion engine. 
 
     
     
       4. The supercharger control device for an internal combustion engine according to  claim 1 , further comprising a unit which adjusts a valve opening speed or a valve opening timing of an exhaust gas switching valve, and adjusts a valve opening speed or a valve opening timing of an intake air switching valve, based on the difference between the target supercharging pressure and the actual supercharging pressure, when the switching control unit switches from the single turbo mode to the twin turbo mode. 
     
     
       5. The supercharger control device for an internal combustion engine according to  claim 1 , further comprising a unit which adjusts a valve opening speed or a valve opening timing of an exhaust gas switching valve, and adjusts a valve opening speed or a valve opening timing of an intake air switching valve, based on a difference between the basic switching supercharging pressure and the target supercharging pressure, when the switching control unit switches from the single turbo mode to the twin turbo mode. 
     
     
       6. The supercharger control device for an internal combustion engine according to  claim 1 , further comprising a unit which adjusts a valve opening speed or a valve opening timing of an exhaust gas switching valve, and adjusts a valve opening speed or a valve opening timing of an intake air switching valve, based on a driving state of the internal combustion engine, when the switching control unit switches the operation mode of the engine from the single turbo mode to the twin turbo mode. 
     
     
       7. The supercharger control device for an internal combustion engine according to  claim 1 ,
 wherein the first supercharger and the second supercharger are arranged in parallel with each other on an intake air passage and an exhaust passage.